/*******************************************************
 *  -------------------------------------------------  *
 *  |  0  |  1  |  2  |  3  |  4  |  5  |  6  |  7  |  *
 *  -------------------------------------------------  *
 *  |     0     |     8     |    16     |    24     |  *
 *  -------------------------------------------------  *
 *  |   t.fctx  |   t.data  |    r2     |    r6     |  *
 *  -------------------------------------------------  *
 *  -------------------------------------------------  *
 *  |  8  |  9  |  10 |  11 |  12 |  13 |  14 |  15 |  *
 *  -------------------------------------------------  *
 *  |     32    |    40     |     48    |     56    |  *
 *  -------------------------------------------------  *
 *  |     r7    |     r8    |     r9    |    r10    |  *
 *  -------------------------------------------------  *
 *  -------------------------------------------------  *
 *  |  16 |  17 |  18 |  19 |  20 |  21 |  22 |  23 |  *
 *  -------------------------------------------------  *
 *  |     64    |     72    |     80    |     88    |  *
 *  -------------------------------------------------  *
 *  |    r11    |    r12    |    r13    |    r14    |  *
 *  -------------------------------------------------  *
 *  -------------------------------------------------  *
 *  |  24 |  25 |  26 |  27 |  28 | 29  |  30 |  31 |  *
 *  -------------------------------------------------  *
 *  |     96    |    104    |    112    |    120    |  *
 *  -------------------------------------------------  *
 *  |     f8    |     f9    |    f10    |    f11    |  *
 *  -------------------------------------------------  *
 *  -------------------------------------------------  *
 *  |  32 |  33 |  34 |  35 |  36 |  37 |  38 |  39 |  *
 *  -------------------------------------------------  *
 *  |    128    |    136    |    144    |    152    |  *
 *  -------------------------------------------------  *
 *  |    f12    |    f13    |    f14    |    f15    |  *
 *  -------------------------------------------------  *
 *  -------------------------------------------------  *
 *  |  40 |  41 |  42 |  43 |  44 |  45 |  46 |  47 |  *
 *  -------------------------------------------------  *
 *  |    160    |    168    |    176    |           |  *
 *  -------------------------------------------------  *
 *  |    fpc    |     pc    |           |           |  *
 *  -------------------------------------------------  *
 *******************************************************/

.text
.align	8
.global	jump_fcontext
.type	jump_fcontext, @function

#define ARG_OFFSET         0
#define GR_OFFSET	   16
#define FP_OFFSET	   96
#define FPC_OFFSET	   160
#define PC_OFFSET	   168
#define CONTEXT_SIZE	   176

#define REG_SAVE_AREA_SIZE 160

/*

typedef void*   fcontext_t;

struct transfer_t {
   fcontext_t  fctx;
   void    *   data;
};

transfer_t jump_fcontext( fcontext_t const to,
			  void * data);

Incoming args
r2 - Hidden argument to the location where the return transfer_t needs to be returned
r3 - Context we want to switch to
r4 - Data pointer

*/

jump_fcontext:
	.machine "z10"
	/* Reserve stack space to store the current context.  */
	aghi	%r15,-CONTEXT_SIZE

	/* Save the argument register holding the location of the return value.  */
	stg	%r2,GR_OFFSET(%r15)

	/* Save the call-saved general purpose registers.  */
	stmg	%r6,%r14,GR_OFFSET+8(%r15)

	/* Save call-saved floating point registers.  */
	std	%f8,FP_OFFSET(%r15)
	std	%f9,FP_OFFSET+8(%r15)
	std	%f10,FP_OFFSET+16(%r15)
	std	%f11,FP_OFFSET+24(%r15)
	std	%f12,FP_OFFSET+32(%r15)
	std	%f13,FP_OFFSET+40(%r15)
	std	%f14,FP_OFFSET+48(%r15)
	std	%f15,FP_OFFSET+56(%r15)

	/* Save the return address as current pc.  */
	stg	%r14,PC_OFFSET(%r15)

	/* Save the floating point control register.  */
	stfpc	FPC_OFFSET(%r15)

	/* Backup the stack pointer pointing to the old context-data into r1.  */
	lgr	 %r1,%r15

	/* Load the new context pointer as stack pointer.  */
	lgr	%r15,%r3

	/* Restore the call-saved GPRs from the new context.  */
	lmg	%r6,%r14,GR_OFFSET+8(%r15)

	/* Restore call-saved floating point registers.  */
	ld	%f8,FP_OFFSET(%r15)
	ld	%f9,FP_OFFSET+8(%r15)
	ld	%f10,FP_OFFSET+16(%r15)
	ld	%f11,FP_OFFSET+24(%r15)
	ld	%f12,FP_OFFSET+32(%r15)
	ld	%f13,FP_OFFSET+40(%r15)
	ld	%f14,FP_OFFSET+48(%r15)
	ld	%f15,FP_OFFSET+56(%r15)

	/* Load the floating point control register.  */
	lfpc	FPC_OFFSET(%r15)

	/* Restore PC - the location where we will jump to at the end.  */
	lg	%r5,PC_OFFSET(%r15)

	ltg	%r2,GR_OFFSET(%r15)
	jnz	use_return_slot

	/* We restore a make_fcontext context.  Use the function
	   argument slot in the context we just saved and allocate the
	   register save area for the target function.  */
	la	%r2,ARG_OFFSET(%r1)
	aghi	%r15,-REG_SAVE_AREA_SIZE

use_return_slot:
	/* Save the two fields in transfer_t.  When calling a
	   make_fcontext function this becomes the function argument of
	   the target function, otherwise it will be the return value of
	   jump_fcontext.  */
	stg	%r1,0(%r2)
	stg	%r4,8(%r2)

	/* Free the restored context.  */
	aghi	%r15,CONTEXT_SIZE

	/* Jump to the PC loaded from the new context.  */
	br	%r5


.size   jump_fcontext,.-jump_fcontext
.section .note.GNU-stack,"",%progbits
